The structures, functions and distributions of receptors and transporters in the e nervous system and neuroendocrine tissues are being studied. Two glycine transporter variants arise from alternative promoter usage and may be developmentally regulated. The distributions of serotonin, dopamine, norepinephrine transporters and vesicular monoamine transporters have been determined using in situ hybridatizaton histochemistry in adult and embryonic rat tissues. Regulation of serotonin transporter function by receptor-activation has been mechanism (including phosphorylation and intracellular trafficking) of these effects continues to b e studied. The gene for the serotonin transporter has been isolated and transcriptional regulation is being studied.